Flexible flat panel display

CLAIM OF PRIORITY

p-0002This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for FLEXIBLE FLAT PANEL DISPLAY DEVICE earlier filed in the Korean Intellectual Property Office on the 14 of Oct. 2005 and there duly assigned Serial No. 10-2005-0096939.

BACKGROUND OF THE INVENTION

p-00031. Field of the Invention

p-0004The present invention relates to a flexible flat panel display, and more particularly, to a flexible flat panel display which prevents electronic units such as a driving Integrated Circuit (IC) and a flexible printed circuit board from being separated from the flexible flat panel display even when the flexible flat panel display is bent.

p-00052. Description of the Related Art

p-0006A flat panel display such as a liquid crystal display, an organic light emitting device, or an inorganic light emitting device has a flat shape and can be used as a flexible display.

p-0007In order to be connected to an external circuit device, the flat panel display is bonded to a flexible printed circuit board. A driving Integrated Circuit (IC) is directly mounted on the flexible display. The flexible printed circuit board or the driving IC is bonded to a pad unit formed on an edge of the flat panel display via an anisotropy conductive adhesive. Alternatively, the flexible printed circuit board or the driving IC is attached to a lateral or longitudinal side of a flat panel display.

p-0008The flexible flat panel display can be bent in at least one direction, and can be used in a bent state. For example, the flexible flat panel display can be bent in a specific direction and attached to a cylinder or the like.

p-0009However, when the flexible flat panel display is bent, the flexible printed circuit board or the driving IC placed on a bent side will likely separate from the flexible flat panel display due to the bending stress. In this case, the flat panel display is electrically open and an image cannot be displayed.

SUMMARY OF THE INVENTION

p-0010The present invention provides a flexible flat panel display in which a flexible printed circuit board and a driving Integrated Circuit (IC) are not separated from the flexible flat panel display even when the flexible flat panel display is bent.

p-0011According to one aspect of the present invention, a flexible flat panel display is provided, the flexible flat panel display including: a flexible display unit including a display area adapted to display an image, a first side and a second side parallel to edges of the display area, and a third side and a fourth side perpendicular to the first and second sides, the third side and the fourth being adapted to being bent; and electronic units arranged solely on at least one of the first and second sides and absent the third and fourth sides. The electronic unit is arranged on the first side and includes a scan driving circuit. The electronic unit arranged on the first side includes a scan driving IC including the scan driving circuit. The electronic unit arranged on the first side includes a scan driving unit including the scan driving circuit and is patterned on the first side.

p-0012The electronic unit is preferably arranged on the second side and includes a data driving circuit. The electronic unit arranged on the second side preferably includes a data driving IC including the data driving circuit. The electronic unit arranged on the second side preferably includes a data driving unit which includes the data driving circuit and is patterned on the second side.

p-0013The electronic unit is alternatively preferably arranged on the first side and includes a flexible circuit board bonded to the first side.

p-0014The electronic unit is alternatively preferably arranged on the second side and includes a flexible circuit board bonded to the second side.

p-0015The electronic unit is preferably arranged on the first side and includes a first scan driving circuit and a first data driving circuit. The electronic unit arranged on the first side preferably includes a first scan driving IC including the first scan driving circuit. The electronic unit arranged on the first side alternatively preferably includes a first scan driving unit including the first scan driving circuit and is patterned on the first side. The electronic unit arranged on the first side alternatively preferably includes a first data driving IC including the first data driving circuit. The electronic unit arranged on the first side alternatively preferably includes a first data driving unit including the first data driving circuit and is patterned on the first side.

p-0016The electronic unit is alternatively preferably arranged on the second side and includes a second scan driving circuit and a second data driving circuit. The electronic unit arranged on the second side preferably includes a second scan drive IC including the second scan driving circuit. The electronic unit arranged on the second side alternatively preferably includes a second scan driving unit including the second scan driving circuit and is patterned on the second side. The electronic unit arranged on the second side alternatively preferably includes a second data driving IC including the second data driving circuit. The electronic unit arranged on the second side alternatively preferably includes a second data driving unit including the second data driving circuit and is patterned on the second side.

p-0017According to another aspect of the present invention, a flexible flat panel display is provided including: a display area adapted to be bent in at least one direction and to display an image; a plurality of first wires intersecting the display area and extending along sides of the display area, the sides of the display area being bent; and a plurality of second wires intersecting the display area and extending along other sides of the display area, the other sides of the display area not being bent; the first wires and the second wires extending along the sides of the display area to locations external to the display area.

p-0018The first wires and the second wires preferably extend in opposite directions external to the display area. The first wires and the second wires alternatively preferably extend in the same direction external to the display area.

p-0019External to the display area, some of the first wires and second wires alternatively preferably extend in one bending direction of the bent sides of the display area, and the other of the first wires and second wires preferably extend in another bending direction different from the one bending direction.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0020A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

p-0021<figref idrefs="DRAWINGS">FIG. 1</figref> is a plan view of a flexible flat panel display according to an embodiment of the present invention;

p-0022<figref idrefs="DRAWINGS">FIG. 2</figref> is a circuit diagram of pixels of an Active-Matrix (AM) organic light emitting display, which is an example of a display area of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0023<figref idrefs="DRAWINGS">FIG. 3</figref> is a cross-sectional view of an example of a portion of the AM organic light emitting display of <figref idrefs="DRAWINGS">FIG. 2</figref>;

p-0024<figref idrefs="DRAWINGS">FIG. 4</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention;

p-0025<figref idrefs="DRAWINGS">FIG. 5</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention;

p-0026<figref idrefs="DRAWINGS">FIG. 6</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention;

p-0027<figref idrefs="DRAWINGS">FIG. 7</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention; and

p-0028<figref idrefs="DRAWINGS">FIG. 8</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

p-0029<figref idrefs="DRAWINGS">FIG. 1</figref> is a plan view of a flexible flat panel display according to an embodiment of the present invention.

p-0030Referring to <figref idrefs="DRAWINGS">FIG. 1</figref>, the flexible flat panel display includes a flexible display unit <b>1</b>, and a first electronic unit <b>2</b> and a second electronic unit <b>3</b> bonded to the display unit <b>1</b>. The flexible display unit <b>1</b>, as shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, can have a rectangular shape, and includes a first side <b>12</b><i>a </i>and a second side <b>12</b><i>b</i>, which are short sides parallel to each other, and a third side <b>12</b><i>c </i>and a fourth side <b>12</b><i>d </i>which are long sides parallel to each other.

p-0031The flexible display unit <b>1</b> can be bent in at least one direction. In the present embodiment, the flexible display unit <b>1</b> can be bent in the arrow directions indicated in <figref idrefs="DRAWINGS">FIG. 1</figref>. That is, the first side <b>12</b><i>a </i>through the fourth side <b>12</b><i>d </i>of the flexible display unit <b>1</b> can be bent, and the flexible display unit <b>1</b> can be used in a state in which the long sides, i.e., the third and fourth sides <b>12</b><i>c </i>and <b>12</b><i>d</i>, are bent.

p-0032A display area <b>10</b> is formed in the center of the flexible display unit <b>1</b>. The display area <b>10</b> can be formed using an Active-Matrix (AM) organic light emitting device, as shown in <figref idrefs="DRAWINGS">FIG. 2</figref>.

p-0033Referring to <figref idrefs="DRAWINGS">FIG. 2</figref>, each pixel of the AM organic light emitting device according to an embodiment of the present invention includes at least two Thin Film Transistors (TFTs), that is, a driving TFT M₁and a switching TFT M₂, a storage capacitor C_stand an Organic Light Emitting Diode (OLED).

p-0034The switching TFT M₂is turned on or off in response to a scan signal supplied to a scan line Scan, and transmits a data signal supplied to a data line Data to the storage capacitor C_stand the driving TFT M₁. The driving TFT M₁determines a current flowing into the OLED from a Vdd line in response to the data signal supplied through the switching TFT M₂. The storage capacitor C_ststores the data signal transmitted through the switching TFT M₂for one frame.

p-0035In <figref idrefs="DRAWINGS">FIG. 2</figref>, the driving TFT M₁and the switching TFT M₂are P type Metal Oxide Semiconductor (PMOS) TFTs, but the present invention is not limited thereto. At least one of the driving TFT M₁and the switching TFT M₂can be an N type Metal Oxide Semiconductor (NMOS) TFT. Moreover, the number of thin film transistors and capacitors is not limited to the above description, and more thin film transistors and capacitors can be included in each pixel.

p-0036<figref idrefs="DRAWINGS">FIG. 3</figref> is a cross-sectional view of an example of a portion of the AM organic light emitting display of <figref idrefs="DRAWINGS">FIG. 2</figref>. Referring to <figref idrefs="DRAWINGS">FIG. 3</figref>, the driving TFT M₁and the OELD are formed on a substrate <b>101</b>. Although the switching TFT M₂and the storage capacitor C_stare not illustrated in <figref idrefs="DRAWINGS">FIG. 3</figref>, they can be formed by the same processes used to form the driving TFT M₁.

p-0037The substrate <b>101</b> can be made of acryl, polyimide, polycarbonate, polyester, mylar, or an other plastic material, but the present invention is not limited thereto. For example, the substrate <b>101</b> can be made of a metal foil, such as Stainless Steel (SUS) or tungsten, or a thin glass. The substrate <b>101</b> is flexible.

p-0038An insulating layer <b>102</b>, such as a barrier layer and/or a buffer layer, can be formed on the substrate <b>101</b> to prevent diffusion of impurity ions and penetration of moisture or air and to planarize a surface of the substrate <b>101</b>.

p-0039An active layer <b>107</b> of the driving TFT M₁is formed of a semiconductor material on the insulating layer <b>102</b>, and a gate insulating layer <b>103</b> is formed to cover the active layer <b>107</b>. The active layer <b>107</b> can be formed of an inorganic semiconductor, such as amorphous silicon or poly silicon, or an organic semiconductor.

p-0040A gate electrode <b>108</b> is disposed on the gate insulating layer <b>103</b>, and an interlayer insulating layer <b>104</b> is formed to cover the gate electrode <b>108</b>. Then, source/drain electrodes <b>109</b> are formed on the interlayer layer <b>104</b>, and a passivation layer <b>105</b> and a pixel defining layer <b>106</b> are sequentially formed to cover the source/drain electrodes <b>109</b>.

p-0041The gate electrode <b>108</b> and the source/drain electrodes <b>109</b> can be formed of a metal, such as Al, Mo, Au, Ag, Pt/Pd, or Cu, but the present invention is not limited thereto. The gate electrode <b>108</b> and the source/drain electrodes <b>109</b> can be coated with a resin paste including a metal powder, or can be formed of a conductive polymer.

p-0042The gate insulating layer <b>103</b>, the interlayer layer <b>104</b>, the passivation layer <b>105</b>, and the pixel defining layer <b>106</b> can be formed as insulators having a single layer or multiple layers formed of an organic material, an inorganic material, or a compound of organic and inorganic materials.

p-0043The layer structure of the driving TFT M₁is not limited to that described above, and the driving TFT M₁can have a variety of layer structures.

p-0044A pixel electrode <b>110</b>, that is, one electrode of the OLED, is formed on the passivation layer <b>105</b>, and the pixel defining layer <b>106</b> is formed on the pixel electrode <b>110</b>. Then, a predetermined opening portion is formed on the pixel defining layer <b>106</b> to exposed the pixel electrode <b>110</b>, and an organic light emitting layer <b>111</b> of the OLED is formed in the open portion.

p-0045The OLED displays a predetermined image by emitting red, green, and blue light according to a current flow, and includes the pixel electrode <b>110</b> connected one of the source/drain electrodes <b>109</b> of the driving TFT M₁, a counter electrode <b>112</b> covering all of the pixels, and the organic light emitting layer <b>111</b> that is interposed between the pixel electrode <b>110</b> and the counter electrode <b>112</b> and emits light.

p-0046The pixel electrode <b>110</b> and the counter electrode <b>112</b> are insulated from each other by the organic light emitting layer <b>111</b>, and the organic light emitting layer <b>111</b> emits light by applying voltages of different polarities.

p-0047The organic light emitting layer <b>111</b> can be a small molecule organic layer or a polymeric organic layer. When a small molecule organic layer is used, the organic layer can be formed by a structure of a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an EMission Layer (EML), a Electron Transport Layer (ETL), an Electron Injection Layer (EIL), or the like, and an available organic material can be copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), tris-8hydroxyquinoline aluminium (Alq3), or the like. The small molecule organic layer is formed by a vapor deposition method.

p-0048In the case of a polymeric organic layer, the organic layer is formed by an HTL and an EML, and the HTL is made of polyethylenedioxythiophene (PEDOT), and the EML is made of a polymeric organic material, such as poly-phenylenevinylene (PPV) group or a polyfluorene group, and is formed by a screen printing or an inkjet printing method.

p-0049The organic layer is not limited to the above description, and can be formed in various ways.

p-0050The pixel electrode <b>110</b> acts as an anode electrode, and the counter electrode <b>112</b> acts as a cathode electrode. However, the functions of the pixel electrode <b>110</b> and the counter electrode <b>112</b> can be reversed.

p-0051In the case of a bottom emission type, the pixel electrode <b>110</b> can be a transparent electrode, and the counter electrode <b>112</b> can be a reflective layer. The transparent electrode can be made of ITO, IZO, In₂O₃, or ZnO, which is transparent and has a high work function, and the reflective layer can be made of a metal, such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals, which has a low work function.

p-0052In the case of a top emission type, the pixel electrode <b>110</b> can be a reflective electrode, and the counter electrode <b>112</b> can be a transparent electrode. In this case, the reflective electrode, that is, the pixel electrode <b>110</b>, is fabricated by forming a reflective layer made of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals and then forming a layer made of ITO, IZO, ZnO, or In₂O₃, which has a high work function, on the reflective layer. The transparent electrode, that is, the counter electrode <b>112</b> is formed in a thin film, by depositing metal with a low work function, that is, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these metals, and then forming an auxiliary electrode layer or a bus electrode line with a transparent conductive material, such as ITO, IZO, ZnO, or In₂O₃.

p-0053In the case of a dual emission type, both the pixel electrode <b>110</b> and the counter electrode <b>112</b> can be transparent electrodes.

p-0054The material of the pixel electrode <b>110</b> and the counter electrode <b>112</b> is not limited to that described above. The pixel electrode <b>110</b> and the counter electrode <b>112</b> can be made of a conductive material or conductive paste containing conductive particles, such as Ag, Mg, or Cu. When the conductive paste is used, the conductive paste can be printed using a inkjet printing method, and after printing, an electrode can be formed by plasticizing the paste.

p-0055After fabricating the OLED, the top of the OLED is sealed to protect it from air.

p-0056Referring again to <figref idrefs="DRAWINGS">FIG. 1</figref>, the scan lines Scan shown in <figref idrefs="DRAWINGS">FIG. 2</figref> extend toward the outside of the display area <b>10</b> and are connected to scan wires <b>14</b>, and the data line Data extends toward the outside of the display area <b>10</b> and are connected to data wires <b>16</b>.

p-0057The scan wires <b>14</b> and the data wires <b>16</b> extend in a bending direction of the flexible display unit <b>1</b>, that is, along bent sides of the flexible display unit <b>1</b>. Specifically, the scan wires <b>14</b> are stretched from the display area <b>10</b> to the third side <b>12</b><i>c </i>and the fourth side <b>12</b><i>d</i>, extend along the third side <b>12</b><i>c </i>and the fourth side <b>12</b><i>d</i>, and form a scan pad on the second side <b>12</b><i>b</i>. The data wires <b>16</b> extend along the first side <b>12</b><i>a </i>and form a data pad on the first side <b>12</b><i>a. </i>

p-0058The first electronic unit <b>2</b> is connected to the data pad formed on the first side <b>12</b><i>a</i>, and the second electronic unit <b>3</b> is connected to the scan pad formed on the second side <b>12</b><i>b</i>. The first electronic unit <b>2</b> can include a data driving IC <b>21</b>, a flexible printed circuit board <b>22</b> on which the data driving IC <b>21</b> is mounted, and a printed circuit board <b>23</b> connected to the flexible printed circuit board <b>22</b>. The flexible printed circuit board <b>22</b> can be bonded to the data pad. The second electronic unit <b>3</b> includes a scan driving IC <b>31</b>, a flexible printed circuit board <b>32</b> on which the scan driving IC <b>31</b> is mounted, and a printed circuit board <b>33</b> connected to the flexible printed circuit board <b>32</b>. The flexible printed circuit board <b>32</b> is bonded to the scan pad.

p-0059Although other signal wires including Vdd wires are not illustrated in <figref idrefs="DRAWINGS">FIG. 1</figref>, the signal wires extend in a bending direction, that is, along the bent sides, and form pads on the first side <b>12</b><i>a </i>and the second side <b>12</b><i>b</i>. Moreover, the signal wires are connected to the first electronic unit <b>2</b> and the second electrode unit <b>3</b>, or an additional electronic unit and provides them with a signal and current.

p-0060According to the present embodiment, as shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, the third side <b>12</b><i>c </i>and the fourth side <b>12</b><i>d </i>are not connected to any electronic units. Therefore, even when the flexible display unit <b>1</b> is bent, the first electronic unit <b>2</b> and the second electronic unit <b>3</b> are not affected by a bending stress, and the first and second electronic units <b>2</b> and <b>3</b> are prevented from being separated from the flexible display unit <b>1</b>.

p-0061<figref idrefs="DRAWINGS">FIG. 4</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention. The flexible flat panel display of <figref idrefs="DRAWINGS">FIG. 4</figref> solves a problem where the pixel response speeds can be different due to the long scan wires <b>14</b>. To this end, a scan section of the display area <b>10</b> is divided into two sections, and a first scan section extends to the first side <b>12</b><i>a </i>via first scan wires <b>14</b><i>a </i>and is connected to a first scan driving IC <b>51</b> of a fourth electronic unit <b>5</b>, and a second scan section extends to the second side <b>12</b><i>b </i>via second wires <b>14</b><i>b </i>and is connected to a second scan driving IC <b>71</b> of a sixth electronic unit <b>7</b>. Hence, a distance difference between the farthest pixel and the closest pixel from each of the scan driving IC can be somewhat reduced, and therefore, voltage drop in the scan lines and differences between response speeds can be reduced. Moreover, in this case, a part of the data line extends to the first side <b>12</b><i>a </i>and is connected to a first data driving IC <b>41</b> of a third electronic unit <b>4</b>, and the other part extends to the second side <b>12</b><i>b </i>and is connected to a second driving IC <b>61</b> of a fifth electronic unit <b>6</b>. The third, fourth, fifth, and sixth electronic units <b>4</b>, <b>5</b>, <b>6</b>, and <b>7</b> includes flexible printed circuit boards <b>42</b>, <b>52</b>, <b>62</b>, and <b>72</b> and printed circuit board <b>43</b>, <b>53</b>, <b>63</b>, and <b>73</b>, respectively.

p-0062The present embodiment is not limited to the above-described electronic units including the flexible printed circuit board on which a scan driving IC or a data driving IC are mounted, and/or the printed circuit board. The electronic units can include a scan driving unit having a scan diving circuit or a data driving unit having a data driving circuit, wherein the scan driving circuit and the data driving circuit are formed by a deposition and patterning method.

p-0063Referring to <figref idrefs="DRAWINGS">FIG. 5</figref>, the first electronic unit <b>2</b> is formed by a data driving unit <b>24</b> including a data driving circuit. Referring to <figref idrefs="DRAWINGS">FIG. 6</figref>, the second electronic unit <b>3</b> is formed by a scan driving unit <b>34</b> including a scan driving circuit. The data driving unit <b>24</b> and the scan driving unit <b>34</b> can be a data driving IC and a scan driving IC. The data driving unit <b>24</b> and the scan driving unit <b>34</b> can include a plurality of PMOS TFTs, NMOS TFTs, or CMOS TFTs. Although not illustrated, each of the first electronic unit and the second electronic unit can formed by a data driving unit including a data driving circuit and a scan driving unit including a scan driving circuit.

p-0064<figref idrefs="DRAWINGS">FIG. 7</figref> is a plan view of a flexible flat panel display according to another embodiment of the present invention. In <figref idrefs="DRAWINGS">FIG. 7</figref>, the third electronic unit <b>4</b> and the fifth electronic unit <b>6</b> are formed by a first data driving unit <b>44</b> and a second data driving unit <b>64</b>, each of which includes a data driving circuit, and the fourth electronic unit <b>5</b> and the sixth electronic unit <b>7</b> are formed by a first scan driving unit <b>54</b> and a second scan driving unit <b>74</b>, each of which includes a scan driving circuit. Although not illustrated, each of the third through sixth electronic units <b>4</b>, <b>5</b>, <b>6</b>, and <b>7</b> can be formed by a data driving unit including a data driving circuit and a scan driving unit including a scan driving unit.

p-0065The present invention is applied not only to a structure in which a scan driving IC and a data driving IC are mounted on a flexible printed circuit board and the flexible printed circuit board is connected to the flexible display unit, but also to a structure in which the scan driving IC and the data driving IC are directly mounted on the first side and/or the second side of the flexible display unit.

p-0066A flexible printed circuit board according to the present invention is applied not only to the organic light emitting display described above, but also to any flexible flat panel display.

p-0067According to the present invention, electronic units such as a flexible printed circuit board and a driving IC are not mounted on sides of a flexible display unit to be bent, but are mounted on sides perpendicular to the bent sides, and thus the electronic units are not affected by a bending stress even when a flexible display unit is bent and the electronic units are prevented from being separated from the flexible display unit.

p-0068While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various modifications in form and detail can be made therein without departing from the spirit and scope of the present invention as defined by the following claims.